In 1774, Abigail Adams — wife of John Adams, who would later be America’s second president — wrote him a letter disparaging Roman Catholics.

“She called Catholics ‘mumbling wretches,’ ” said Robert Destro of Catholic University of America’s Columbus School of Law. “But nobody was going to compel her to go to one of those churches, and she couldn’t compel anybody not to do any of that ‘mumbling.’ ”

The framers of the Constitution were adamant about separating church and state. They made it the First Amendment.

The argument over what religious freedom means is hardly new to Americans.

Religious-freedom measures sponsored by opponents of same-sex marriage that recently passed in Indiana and Arkansas triggered fierce protests from gay-rights groups, which led lawmakers to roll back some of the legislation. On Thursday, Indiana Governor Mike Pence approved a new version that bars discrimination based on sexual orientation.

Still, the controversy has been a reminder that the principle of religious freedom hasn’t always been easy to uphold.

Mormons got to know that firsthand in the mid-18th century, when the federal government almost went to war against them. The so-called “Utah War” was — except for some skirmishes and a massacre by Mormons — averted when the Church of Jesus Christ of Latter-day Saints agreed to abandon polygamy.

In 1990, the Supreme Court ruled that members of an Indian tribe in Oregon who took part in a religious ritual involving the banned narcotic plant peyote could be fired from government jobs. That was the straw that prompted faith groups and constitutional scholars, such as Destro, to feel that religious freedom needed a boost.

“I’ve been litigating First Amendment cases for years, and it was always, if you look at the cases, religious liberty almost invariably lost those cases,” he said.

He helped Congress formulate the Religious Freedom Restoration Act, signed by former President Bill Clinton in 1993. Since that law applied to the federal government, states began passing their own versions of RFRA.